Printing by transfer-sublimation, i. e. by means of sublimable dyes, is already known, and it can be described as the printing, in a first step, of designs on a paper substrate by using inks constituted by sublimable dyes, capable of vaporizing when reaching a certain temperature and of fixing themselves permanently on certain synthetic fibers, whereas different methods can be used for printing the paper substrate, for instance offset, flexography- or heliography-printing, or flat-bed or rotary screen-printing. Then, in a second step, the pre-printed designs of sublimable dyes--as applied on the paper substrate--are transferred by contact under predetermined pressure and temperature between the printed paper and the fabric to be decorated.
This method of transfer-sublimation is currently used for printing on synthetic fabrics as well as on the surface of flocked fabrics which are commonly used for upholstery or automobile decoration.
However, this method has never been used for the printing of thermoadhesive or high-frequency-weldable flocked films, because the thermal sensitivity of such films makes it very difficult to print by transfer-sublimation, as this operation must be carried out at a minimum temperature of 180.degree. C. (350.degree. F.), which is a temperature that those films are unable to stand.
Furthermore, thermoadhesive or high-frequency-weldable films are commonly flocked with fibers made of rayon-viscose, which fibers cannot be printed satisfactorily by the existing method of transfer-sublimation.
Thermoadhesive or weldable flocked films are commonly used for the decoration of garments, fabric products and accessories, and more generally of all substrates suitable for decoration by means of heat-application or high-frequency (HF) welding.
Those thermoadhesive or weldable films are usually flocked with fibers which are dyed before flocking, which leads to one-color flocked surfaces in which patterns like numbers, letters or logos are cut out before being applied onto the substrate to be decorated.
For printing multicolored designs on a thermoadhesive or HF-weldable film, usually a screen-printing of a white-colored flocked film is carried out. Generally, white flock-fibers made of rayon-viscose are used. The thermoadhesive or HF-weldable flocked film which is screen-printed in this way with multicolor-designs is usually pre-cut before heat application in case of a thermoadhesive film, and cut out during application in case of HF-welding.
However, this screen-printing method presents some drawbacks, in particular a low washing fastness of the printed colors which are losing their brightness after several washings of the decorated substrate, as well as a low abrasion resistance of the rayon-viscose flock-fibers, mostly when being wet. Also the screen-printing of the flock-layer requires the deposit of an important amount of printing-ink in order to cover the full length of the fibers, which in its turn also requires the use of screens with open mesh, limiting therefore the accuracy of the printing and making impossible the reproduction in four colors and halftones, like for instance photographic works.
In order to obtain a HF-weldable multicolor flocked-film, the use of another method is known where different pre-died nylon flock-fibers are applied by "multicolor-flocking", color by color, each fiber/color going through separate screens and being fixed onto a HF-weldable film, each screen being made according the position of each color in the final multicolor design to be printed on the film. However, this method requires the use of one separate screen for each printed color, and for each printed design, which makes this production of flocked sheets slow and technically difficult, and consequently expensive.